1. Field of the Invention
This invention relates to refractories and particularly porous foamed ceramic insulating refractories and the method of producing these refractories. Insulating refractories are known in the art and are generally lightweight with relatively high porosity to provide thermal insulation for a furnace or kiln.
It is conventional practice to produce ceramic insulating refractories by using one of the following methods of introducing porosity: (1) by incorporating in the refractory material combustible particles which will be burnt out during firing thereby leaving voids, (2) by injecting air into a slurry of refractory particles or (3) by generating a gas in a slurry by means of a chemical reaction.
The selection of the ingedients which go into a particular refractory structure is and has been the subject of much study and experimentation and is in the purview of one skilled in refractory or ceramic art. A combination of inorganic refractory ingredients which is ideal for one use with a specific set of operating variables may be entirely unsuitable for another use or for a similar use with different operating conditions.
2. Description of the Prior Art
U.S. Pat. No. 3,944,425 (Magder) describes a fired refractory composed of clay, hydraulic cement, inert particulate lamellar foam stabilizer, water, and a gas generating agent. The agent preferred for foams intended for refractory use is the combination of hydrogen peroxide and a transitional metal oxide catalyst. Catalyzed hydrogen peroxide or an acid-carbonate combination is suggested for clay foam building products.
U.S. Pat. No. 3,565,647 (Magder) discloses a method of making a cellular material by subjecting the ingredients; clay, hydraulic cement, inert particulate lamellar foam stabilizer, water, and a gas generating agent to high-shear mixing in a container for a short period of time before discharging the material and allowing it to foam and set.